This invention relates to novel β-hydroxyalkylamides, a method for their production and their use.
β-hydroxyalkylamides are very important as intermediate products and as cross linkers for polymers. β-hydroxyalkylamides are conventionally produced by the amionlysis of alkyl esters with β-alkanol amines in the presence of basic catalysts. The β-hydroxyalkylamides are isolated and purified either by crystallization in a solvent or, especially with solid β-hydroxyalkylamides, without the use of solvent in a slurry process. A process of the above referenced type is described in U.S. Pat. No. 5,101,073 and in EP 0 473 380 B1. The slurry process is based on the fact that the equilibrium reaction that occurs during the production of the β-hydroxyalkylamides is shifted toward the desired end product as a result of the fact that the desired β-hydroxyalkylamide is precipitated from the melt by tempering in a defined temperature range and the melt is then crystallized. A disadvantage of this method is the use of equimolar quantities of alkyl ester and β-hydroxyalkylamide.
An additional process for the production of β-hydroxyalkylamides is described in DE 198 23 925. In this method, the ester is converted without the use of solvents with the alkanol amines in the presence of basic catalysts.
EP-A-322 834 describes a powder coating which contains a polyester and β-hydroxyalkylkamides as cross linkers (curing agents). Corresponding coatings with good characteristics can be produced with the formulation described in said document.
On account of the major importance of β-hydroxyalkylamides as an intermediate product, especially as cross linkers for polyester powder coats as disclosed EP-A-322 834, there has recently been a great deal of interest in new and innovative β-hydroxyalkylamides.
On the basis of the prior art described above, the object of this invention is to propose new, previously unknown β-hydroxyalkylamides and a corresponding process for their production.
The invention teaches that this object can be accomplished with regard to the β-hydroxyalkylamides by utilizing a β-hydroxyalkylamide having the general Formula I:
wherein R1 is H or a linear or branched C1 to C10 alkyl and R2 is a linear or branched C1 to C5 alkyl to cross-link a polymer.
The β-hydroxyalkylamide claimed by the invention is defined by the general Formula I.

In Formula I, R1 stands for hydrogen or a linear or branched C1 to C10 alkyl. R2 is a linear or branched C1 to C5 alkyl. The β-hydroxyalkylamides claimed by the invention are characterized in particular by the substituted carbon atom next to the OH group. In the β-hydroxyalkylamides claimed by the invention, the R2 group is located here.
The β-hydroxyalkylamide is preferably constructed so that the R1 group is H, tert-butyl, isopropyl or pentyl and is located in the para position to the CO group.
One particularly advantageous realization of the invention is characterized by the fact that the R1 group is hydrogen and the R2 group is methyl.
These β-hydroxyalkylamides are produced by converting a carboxylic acid derivative having the general Formula II.
with an alkanol amine having the general Formula III.

The R1 and R2 groups thereby have the definitions presented above. The R3 group can thereby be a halogen, preferably chlorine, or an OR4 group. If there is an OR4 group, R4 is a linear C1 to C5 alkyl, preferably a —CH3 group.
The conversion of the carboxylic acid derivative and the alkanol amine preferably takes place in a solution. Preferred solvents include but are not restricted to: aromatic hydrocarbons such as benzene, toluene or xylene. Ethers such as diethylether or mixtures of the solvents listed above are also suitable.
An essential feature of the process claimed by the invention is that the carboxylic acid derivative having the general Formula II and the alkanol amine having the general Formula III are reacted with vigorous agitation of stirring. The alkanol amine is thereby preferably presented first and the carboxylic acid derivative is then added by drops with vigorous agitation of stirring.
For the case of the carboxylic acid halide, the conversion takes place at −10 to 25° C., preferably at 0 to 10° C. The reaction time is normally 0.5 to 5 hours. A reaction time of 2 hours is most advantageous.
If esters are included in the process (R3=OR4), the reaction temperature at RT is up to 150° C.
The β-hydroxyalkylamide is particularly well suited as a cross linker for polymers. β-hydroxyalkylamide is particularly preferred as a cross-linker for powder coats with polyesters or acrylates as the polymer.
Basically, the β-hydroxyalkylamide can be used as a cross linker (curing agent) analogous to the β-hydroxyalkylamides cited in EP-A-322 A34. The β-hydroxyalkylamides taught by the invention can also be used in combination with other curing agents. One example of this usage is the curing agent sold under the name PRIMID® by EMS-CHEMIE AG, Domat/Ems. PRIMID® is N,N,N′,N′ 2-hydroxyethyladipamide.
The invention is explained in greater detail below with reference to one example of production for the preferred embodiment of the invention, in which R1 is H and R2 is CH3.